JPS5833164B2 - Hollow granular percarbonate and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hollow granular percarbonate having a novel shape and structure and a method for producing the same.

More specifically, we need a stable hollow granular percarbonate that has a high dissolution rate, has the ability to dissolve without leaving any dissolution residue, and has little loss of effective oxygen even when stored for a long period of time, and has such characteristic properties. The present invention relates to a method for producing hollow granular percarbonate having the following properties.

Moreover, since the percarbonate is in the form of hollow granules, it has excellent dehydration properties of slurry during production and powder physical properties as a product.

In general, percarbonates are often used alone or in combination with surfactants, etc., as oxygen-based bleaching agents that do not emit bad odors or harmful gases.

Its bleaching blade is milder than chlorine-based ones, and it is preferred because it provides a well-balanced bleaching effect on colors, patterns, etc.

For bleaching fabrics, especially colored and patterned fabrics, it is not only necessary that the bleaching blade be moderate, but it is also essential that the bleaching blade work equally on all parts of the fabric.

Otherwise, unevenness and localized discoloration will occur, which will greatly reduce the value of the fabric.

Percarbonates are usually prepared in powder, spherulite or granular form and are used in a number of aqueous solutions.

If the percarbonate is not completely dissolved when the fabric is immersed in this aqueous solution, the percarbonate particles will adhere to the fabric and cause selective bleaching there, resulting in uneven color and, in extreme cases, Causes wear and tear on the fabric.

If the fabric is continued to be stirred after dipping, this problem will not occur, but in most cases, the fabric is used by dipping and then allowing it to stand still.

Therefore, to prevent this, it is extremely important to homogeneously dissolve the percarbonate.

When the diameter of the secondary particle of percarbonate crystal exceeds 1.
The rate of dissolution is very slow, so the solution must be stirred for several minutes or particularly hot water must be used to achieve complete dissolution.

In order to eliminate this inconvenience, it is possible to use percarbonate microcrystals.

In order to make the dissolution rate sufficiently fast, the crystallite particle size must be 1
Must not exceed 00μ.

However, it is extremely difficult to handle percarbonate having such crystallites.

In other words, the storage, transportation, and filling of fine powders that decompose exothermically, such as percarbonates, are always dangerous and difficult1, and even when used, the fine powders may irritate the throat and nose. cannot be avoided.

In order to improve the handling properties of such microcrystalline percarbonate, the granulation method disclosed in Japanese Unexamined Patent Publication No. 50-84500 has been devised; The difficulties in handling during manufacturing, ie, dehydration, drying, etc., have not been improved in the slightest.

Therefore, the present inventors conducted intensive research to obtain a percarbonate that has the contradictory properties of thickening the percarbonate particles and having a high dissolution rate, without reducing the dissolution rate in the slightest. The inventors discovered percarbonate aggregates and a new method for producing such aggregates by crystallization, and completed the present invention.

That is, the present invention provides hollow granular percarbonate particles whose insides are hollow and whose shell portions are composed of crystalline percarbonate, and furthermore, as a method for producing the same, carbonate is prepared in 6. 0 to 15.0% by weight and 1.0 to 15.0% by weight of hydrogen peroxide.
An aqueous mother liquor solution containing 5 to 6.0 wt. Crystallizing the percarbonate by adding granular carbonate and an aqueous hydrogen peroxide solution simultaneously or alternately at a ratio such that the carbonate is maintained within a range of 2 moles or more per 3 moles of hydrogen oxide. The present invention provides a method for producing hollow granular percarbonate characterized by the following.

The method for producing hollow granular percarbonate of the present invention will be explained in more detail using sodium percarbonate as an example.

In the case of IJium (percarbonate), the hollow granular particles of the present invention are produced only in the vicinity of point B shown in FIG.

Figure 1 is a triangular diagram showing the phase diagram of the Na2C03-H202H203 component system, and point B is Na2CO3,1,5.
This point indicates a saturated solution of crystal (PC) having the composition H202, and has the composition exemplified in Table 1 when there is no influence of coexisting salts.

Table 1 Na2CO3 and H2O2 concentration at point B (including coexisting salts)
temperature, (ONa2CO3 (wt%) H2O2 (wt%)
57.8 10 8.1 15 8.4 20 8.7 25 9.0 30 9.7 3.75 3.90 4.04 4.19 4.33 4.60 Mother liquor composition is more H2O2 than point B If enriched, no hollow particles will be produced.

For example, at 20℃ Na2CO36.0%, H2O
When Na 2 C03 granules and H2O2 solution are simultaneously added to the mother liquor using the composition at point 0 in Figure 1, which indicates 221.2%, unreacted Na 2 C0 is produced.
It is a granule in which microcrystals of IJium are crystallized, with 3 as the core and percarbonate on the surface.

Since it contains unreacted Na2CO3, the effective oxygen concentration is low, it is hygroscopic, and the particle dissolution rate is significantly slower than that of hollow granules.

If the mother liquor composition exceeds a certain limit from point B, N a 2 C03
Similarly, hollow granules are not produced when the granule is rich in .

For example, at 20°C Na2 CO3 22.0%, H
Point A in Figure 1 showing 2021,4fb was selected as the mother liquor,
When a similar operation is applied, what is produced is simply microcrystals of soda percarbonate.

For this reason, it is extremely difficult to filter the crystals, and drying them is also not easy.

Since it is a microcrystal, the dissolution rate of the formed crystal is good and the amount of effective oxygen is close to the theoretical value, but it has little practical value when considering the powder properties.

Therefore, the mother liquor region produced by the hollow granular soda percarbonate of the present invention is within a very limited range, and the range is (the same below the weight percent unit C), and the Na2CO3 content is 6.0 to 15. Ofo, H2O2 must be in the range of 1.5 to 6°o%, and N to 3 moles of H2O2
It is essential that a2CO3 is in a range of 2 moles or more.

Furthermore, in this range, N a 2 C03 is 7.0 to 13.0
%, H2O2 preferably ranges from 3.0 to 5.0, and N a 2 C03 preferably ranges from 8.0 to 11.5, H
The most preferred range is 2O2 of 3.5 to 4.5.

When adding Na2CO3 and H2O2, the addition ratio must be adjusted so that the mother liquor aqueous solution composition is always maintained within this concentration range, but as long as these conditions are satisfied9, even if both are added at the same time, They may be added alternately, continuously, or intermittently.

However, from the viewpoint of accuracy of concentration adjustment, Na 2 C
The most preferred method is to add 03 and H2O2 simultaneously and continuously.

Regarding the addition rate, Na 2 C0 at the drop point
The velocity must not be such that the three particles do not agglomerate and the composition of the mother liquor near the drop point enters an unfavorable region and does not return to its original state immediately by stirring the system.

As the mother liquor composition changes from point A to point B to point C as described above, the crystal form of the generated soda percarbonate changes greatly due to the dissolution rate of Na 2 COa, the precipitation rate of sodium percarbonate, and the length of the induction period before precipitation.

The curve shown in FIG. 1 is at equilibrium, and it is considered that equilibrium is not established in a system such as water droplets in which Na2CO3 and H2O2 solutions are constantly added.

On one side of the system there is a solution of Na2CO3 and on the other side a precipitate of sodium percarbonate, with a temporary supersaturation state in between.

If we look at this microscopically, we can see that Na2CO was added a long time ago.
3 granules dissolve into the mother liquor from the surface.

Compared to the dissolution of Na 2 CO3, the dissolution and diffusion of H2O2 is so fast that it is not a problem, so it can be safely assumed that the H20□ concentration is almost uniform throughout the system.

On the other hand, dissolved Na2CO3 diffuses from the particle surface toward the offshore.

The heat of dissolution is transferred to the surroundings by diffusion, and after a certain induction period, sodium percarbonate crystals are precipitated.

The length of this lag period depends on the degree of supersaturation.

At the aforementioned point A, the concentration of H2O2 in the offshore mother liquor is dilute and the degree of supersaturation is low.

Therefore, the induction period in sodium percarbonate precipitation 1 becomes longer,
During this time, the diffusion surface of Na2Co3 collapses to such an extent that the original particle external shape is no longer retained.

Particularly, the rapidity of this collapse is noticeable when the system is vigorously agitated.

The resulting precipitate becomes extremely fine crystals.

On the other hand, at point C, since the concentration of H2O2 in the offshore mother liquor is high, even if Na2C03 is slightly eluted, its degree of supersaturation becomes large, and the induction period for precipitation of sodium percarbonate becomes extremely short.

Therefore, a sodium percarbonate film is formed immediately on the surface of Na2CO3.

Once the sodium percarbonate film is formed, Na2CO3
The intrusion of water to dissolve the Na2CO3 solution and the leaching of the Na2CO3 solution are inhibited, and further reactions occur, resulting in K<.

The resulting crystals are granules with unreacted Na2CO3 as the core and sodium percarbonate crystallized on the surface.

Near point B, the rate of Na2CO3 elution and the induction period until precipitation of sodium percarbonate are extremely well balanced.

That is, sodium percarbonate is precipitated while the diffusion surface of the eluted Na2CO3 does not destroy the original granule shape, but voids are created between the Na2C03 surface of the core and the sodium percarbonate precipitation surface. Water ingress and Na2CO3 leaching are not inhibited.

For this reason, microcrystals are precipitated on the inside and outside of the sodium percarbonate precipitation surface, and the sodium percarbonate layer becomes thick.

In this way, the elution of the core Na2CO3 particles is completed to the end, and as a result, complete hollow sodium percarbonate granules are produced.

The greatest feature of the method of the present invention is that the raw material core Na2
The key to this is the technique of precipitating the soda percarbonate microcrystals at just the right location so as not to disturb the diffusion surface where CO3 dissolves and diffuses into the mother liquor.

In addition, from the viewpoint of the formation mechanism of such hollow granules, the stirring conditions of the system, the particle size of the raw material granules, the addition rate, etc. are important factors.

On the other hand, the concentration of the H2O2 solution added and the crystallization temperature hardly matter.

That is, another important requirement in the method of the present invention is that
The point is that granular soda carbonate having a certain size range is added together with an aqueous hydrogen peroxide solution.

As is clear from the above explanation, in the method of the present invention, soda percarbonate crystals grow on the outside of the added soda particles (although some of them also grow inward).
The diameter of the obtained hollow granular soda percarbonate is slightly larger than the diameter of the raw material soda carbonate, and the hollow portion inside has a diameter that is the same as or slightly smaller than the diameter of the raw material soda carbonate.

Therefore, in order to obtain such sodium percarbonate, the granular soda carbonate as a raw material must have a diameter in the range of 50 to 2000 microns (A), preferably 100 to 1000 microns.

If it is less than 50μ, sufficient hollow granules cannot be obtained;
If it exceeds μ, it will be difficult to form a hollow shape in which the soda carbonate inside is completely dissolved.

Note that the shape of the granular soda carbonate does not have to be spherical, and may be any shape such as a cube, a rectangular parallelepiped, or the like.

Regarding the stirring speed, the Raynozzle number (Re) is preferably 100,000 or less, preferably 30,000 or less.

The generated percarbonate slurry can be extracted from the crystallization system at any time.

In other words, there are a completely continuous method in which the slurry is constantly extracted, a semi-continuous method in which the slurry is extracted in small portions, and a batch method in which a certain amount of sodium percarbonate is precipitated and then the entire amount is extracted. .

The concentration of the formed sodium percarbonate crystals in the mother liquor is also an important factor.

If this is too high, Na 2 during crystallization of percarbonate sorb
The COs diffusion surface becomes easily disturbed, and the produced granules collide with each other, causing crushing and increasing the generation of fine powder.

This upper limit concentration is 40 wt%, preferably 3 ow
t% or less.

Although there is no logical lower limit, it is preferably not less than iowt% because it is practically related to the size of the device.

Although the formation of the hollow granules described above is completed within a few minutes, it is desirable to further ripen for about 10 minutes to 3 hours.

This prevents obstruction of filtration due to extremely fine crystals generated in the bulk, acceleration of generation and decomposition of dust, and completes the reaction of unreacted Na2CO3.

When the slurry is extracted semi-continuously or continuously from the crystallizer, it is efficient to provide a separate ripening device.

In that case, the average residence time in the crystallizer is 10 minutes to 3 hours, preferably 30 minutes to 2 hours, and the average residence time in the ripening device is 10 minutes to 3 hours, preferably 30 minutes to 1 hour. It is preferable to provide time.

In that case, by keeping the temperature in the ripening device within 50° C., preferably by 5 to 15° C., lower than the temperature in the crystallizer, decomposition of H2O2 in the mother liquor is suppressed and favorable results are produced.

Furthermore, due to the temperature difference, new sodium percarbonate crystals are precipitated on the surface of the hollow sodium percarbonate, increasing the thickness and improving the particle concentration.

Furthermore, when removing the amount of heat generated during crystallization, it is possible to place part of the load on the component analyzer, thereby improving cooling efficiency.

In the continuous and semi-continuous crystallization described above, in order to simultaneously control the residence time, the concentration of sodium percarbonate crystals in the mother liquor, and the composition of the mother liquor, it is necessary to control the addition rate of Na2CO3 and H2O2, and the rate of precipitation of the soda percarbonate slurry. alone is not enough.

Therefore, water or mother liquor of a certain composition can be mixed with H202, Na2
It must be added to and removed from the crystallizer independently along with CO3.

The most effective way to control this is to recycle the f liquid generated during dehydration of the slurry that has undergone crystallization and aging.

Furthermore, if measures are taken to increase or decrease the amount of mother liquor in the recycling flow as necessary, the mass balance of the system can be achieved.

Furthermore, if patch crystallization is to be performed, the composition and amount of the dehydrated P solution may be corrected as necessary before proceeding to the next cycle.

When recycling this slurry dehydrated mother liquor, lowering its temperature further than that of the aging tank is effective as described above in the sense of preventing the decomposition of sodium percarbonate in the mother liquor and dispersing the heat load of crystallization. .

However, if the temperature difference becomes too large, new hydrated salt crystals of sodium percarbonate or Na2CO3 will be generated, making handling difficult.

The temperature difference with the aging device should be within 20°C, and the weight of the vehicle should be within 10°C.

As described above, the method for producing hollow granular percarbonate of the present invention is based on a completely new principle unknown until now, and the granular percarbonate obtained is hollow inside the particle.
Since it is obtained by direct crystallization, the shell portion of the particle is composed of crystalline percarbonate, and has a structure in which grown percarbonate crystals aggregate.

The state of crystals varies depending on the conditions under which they are formed, but
When silicates are added as a crystal habit modifier, needle-like crystals are obtained, and when aminopolycarboxylic acid salts are added, plate-like crystals increase.

The size of the percarbonate depends on the size of the granular carbonate added, but one with an average particle size of 100μ to 2000μ can be obtained satisfactorily.

Since the hollow granular percarbonate of the present invention has a crystalline hollow structure, it is extremely easy to dehydrate and handle the particles. The dissolution rate is extremely fast compared to granular crystals, and the time for complete dissolution is approximately 1/1 of that of normal granular percarbonate.
3 to 115.

A method for producing percarbonate by crystallization similar to the method of the present invention is the method described in British Patent No. 568,754.

This method is similar in that sodium percarbonate is obtained by simultaneously or alternately adding anhydrous or crystalline sodium carbonate and an aqueous hydrogen peroxide solution to the mother liquor, but the composition of the mother liquor to be crystallized is completely different from that of the present invention. It does not require that the added soda be in the form of particles of a certain size, nor does it take into account the characteristic technique of the present invention as described above. It is inconceivable to see the generation of crystalline hollow particles of the invention.

When producing hollow granular percarbonate based on the new principle described above, phosphates such as sodium tripolyphosphate and sodium metaphosphate, or silicates such as sodium metasilicate are added as stabilizers for the percarbonate. However, in addition to these stabilizers, magnesium salts, preferably 1.
Alternatively, when combined with magnesium sulfate, the stabilizing effect of percarbonate increases synergistically, and its effect increases with the concentration added.

However, there is an upper limit to the concentration of stabilizer added.

In other words, for silicates, the addition concentration is 250
When the carbonate concentration is more than mmol SiA9, a large amount of acicular microcrystalline percarbonate will be generated in addition to hollow granules, and the dehydration properties of the slurry and the powder physical properties of the percarbonate will deteriorate.

Further, when the concentration exceeds 500 mmol Si/kg carbonate, the dissolution rate of the percarbonate granules becomes extremely slow, and the original characteristics are completely lost.

Also, in the case of phosphates, the same thing as silicates occurs at 500 mmolP/lcg carbonate 1.

If this is exceeded, unlike in the case of silicates, the formation of hollow granules is inhibited, but the same is true in the sense that the characteristics of water droplets are lost.

From these facts, the amount of silicate and/or phosphate added is 500 mmol Si and/or P/9 carbonates or less; vehicle weight is 20 to 100 mmol Si
and/or P/ is preferably in the range of 9 carbonates.

It is known that increasing the amount of magnesium salt added results in the formation of insoluble matter, which has undesirable effects.

Therefore, in carrying out the present invention, the amount of magnesium salt added should be 150 mmol 1 MIA9 carbonate or less, preferably 10 mmol
~50 mmol M? It should be in the range of A9 carbonate.

As described above, the stability of percarbonate improves as the amount of these stabilizers increases, but when the amount of stabilizers added is large, the production of hollow granular percarbonate of the present invention becomes difficult. In this case, there is an unfavorable tendency that the shape and crystallinity become easily disordered and the dissolution rate decreases.

In such a case, Na, Ca, or M2 salts of ethylenediaminetetraacetic acid (hereinafter referred to as EDTA) are added to the reaction system to prevent crystallization of percarbonate.
Alternatively, the above-mentioned drawbacks can be improved by carrying out the reaction in the presence of Mt salt.

That is, the decrease in crystallinity due to the addition of a large amount of stabilizer is suppressed, and at the same time, the dissolution rate is restored to the value when a small amount of stabilizer is added.

That is, such Na, Ca or Mt salts of EDTA act as a kind of crystal habit modifier, and change the crystallinity of percarbonate to make it highly soluble again. Addition concentration is 0.5 to 25 depending on the addition concentration of stabilizer.
0 mol Ag carbonate, more preferably 2 to 50 mmo
A range of lA19 carbonates is effective.

Regarding these EDTA salts, percarbonate is conventionally known as a stabilizer, but this seems to suggest that it works to improve the crystallinity of hollow granular percarbonate as used in this method. This phenomenon is not known.

In water droplets, it is clear that the primary purpose of its use is to improve the crystallinity of percarbonate, and not merely as a stabilizer, as has been exemplified.

Next, the present invention will be explained by examples.

Example 1 A mother liquor of 408.1% consisting of 8.8wt% soda carbonate, 4.4wt% hydrogen peroxide, and the balance water. @ 50% hydrogen peroxide solution 131.0. @ and granular anhydrous soda carbonate passed through 70 meshes and remained at 100 meshes 118.3. were added simultaneously and continuously at a constant rate over a period of 30 minutes.

During this time, using a stirring blade with a diameter of 6cIrL, the rotation rate was 33.8rp.
Stirring was continued at a speed of m.

The Reynolds number at this time was 2.0×103.

. Further, external cooling was controlled so that the mother liquor temperature was 20.0±0.1°C.

After the addition of hydrogen peroxide and soda carbonate was completed, the mixture was further aged for 15 minutes under the same conditions.

When this slurry was dehydrated by centrifugation at 900G for 3 minutes,
182.4. The concentrations of hydrogen peroxide and soda carbonate in the @ cake and the zero recovered mother liquor from which 424.89 recovered mother liquors were obtained were 4.58 and 7.21 wt, respectively.

The cake was air-dried at 60°C for 2 hours to a temperature of 153.0. White crystalline granules of @ were obtained.

Most of the obtained granules were hollow, and a mixture of crystalline fine powder and agglomerated particles thereof was observed in some parts.

The particle size distribution of the granules is shown in FIG. 2 (shaded graph).

The figure also shows the particle size distribution of the raw material soda carbonate.

The weight average particle size of the raw material soda carbonate was 180μ, whereas the obtained soda percarbonate granules had a weight average particle size of 240μ.

In addition, the effective oxygen concentration is 14.7%, the apparent density is 0,
It was 45f/CrfL3.

2 tons of these granules were placed in a petri dish with a diameter of 5 cIrL for 20 r.
When it was dissolved in nl of water with stirring, it took 27 seconds for complete dissolution.

At this time, the water temperature was 20°C, and the stirring rod had a length of 3 CII, 11 mm, and a diameter of 0.
6cIrL rotor, stirring speed ij, 300 rpm.

On the other hand, when we measured the dissolution time of commercially available sodium percarbonate (average particle size 220μ, apparent density 0.729/CrIL3 Nakazuma 9 granular sodium percarbonate) under the same conditions, we found that it was 165 seconds. I needed it.

Example 2 To 424 tons of mother liquor consisting of 9.6 wt% of soda carbonate, 4.4 wt% of hydrogen peroxide, and the balance water, 6% of hydrogen peroxide aqueous solution was added.
2.1. @ and granular anhydrous soda carbonate passed through 24 meshes and remained at 32 meshes 16.5. The concentration of soda carbonate in the mother liquor is 9.2-10.5%, and the concentration of hydrogen peroxide is 3%.
．． Na2CO in a proportion that maintains the ratio between 8 and 4.5.
3 per time, 2.55. @, 58 hydrogen peroxide same <2.07. @, divided into 3 and 0 times each, alternately 6 times
L7 was added into the mother liquor over a period of 0 minutes.

During this time, stirring was continued at a speed of 83.5 rpm using a stirring blade with a diameter of 6 (m).

The Reynolds number during stirring was 1.0 x 10'.

In addition, the mother liquor is constantly cooled to 25.0+ by external cooling.
The temperature was controlled to be 0.1°C.

After the addition of the hydrogen peroxide solution and soda carbonate was completed, the mixture was further aged for 30 minutes at the same temperature and stirring speed.

The resulting slurry was dehydrated by centrifugation at 900G for 3 minutes and the result was 95.5. A cake of @ and a recovered mother liquor of 451.7 @ were obtained.

The concentrations of hydrogen peroxide and soda carbonate in the recovered mother liquor were each 4
．． They were 05 and 10.15wt.

When the cake was dried with ventilation at 60℃ for 2 hours, the result was 78.3
White crystalline granules of f were obtained.

A scanning electron micrograph of a typical granule among these (magnification: 1
00 times) are shown in FIGS. 5 and 4.

FIG. 3 is a plan view, and FIG. 4 is a cross-sectional photograph.

This material was found to be sodium percarbonate based on the X-ray diffraction pattern.

Its effective oxygen concentration is 13, s%, and the weight average particle size is 480.
μ, apparent density was 0.44 f/cm3.

Further, when the dissolution time was measured using the same method as in Example 1, complete dissolution occurred in 61 seconds.

Comparative example 1 Soda carbonate 22. owt%, hydrogen peroxide 1.4wt%,
To 416 @ of the mother liquor (point A in Figure 1) consisting of the remainder water, 75.29 tons of 5° preferential hydrogen oxide aqueous solution and 85.9 tons of granular anhydrous soda carbonate that passed through 24 meshes and remained on 32 meshes were continuously added at a constant speed for 60 minutes. and added at the same time.

During this time, stirring was continued at a speed of 169 rpm using a stirring blade of diameter 6 and 771.

The Reynolds number during stirring was 1.0×104.

In addition, by external cooling, the temperature of the system can be reduced to 25.0±0.1℃.
was held at

After the addition of the hydrogen peroxide solution and soda carbonate was completed, the mixture was further aged for 60 minutes.

When this slurry was dehydrated by centrifugation at 900 G for 3 minutes, the result was 195.6. @ cake and 368.7. A recovered mother liquor of @ was obtained.

The concentrations of hydrogen peroxide and soda carbonate in the recovered mother liquor were 1.92 wt and 19.3 wt, respectively.

The cake was air-dried at 60° C. for 2 hours and 136.5. A white powder of @ was obtained.

The powder consisted of microcrystals and no hollow granules were present.

The effective oxygen concentration is 11. r%, average particle size of primary particles is 80
It was less than μ.

The apparent density of the casing was 0.37 f/cm3.

Comparative example 2 Soda carbonate 6, owt%, hydrogen peroxide 21.2wt'%
, the remainder consisting of water (point C in Figure 1) 424.0. @58 Hydrogen peroxide solution 107.2. @, 70 meshes passed, 100 meshes remaining granular anhydrous soda 84.2
p was simultaneously added at a constant rate over 60 minutes.

During this time, using a stirring blade with a diameter of 6 crrL, the rotation rate was 11.5 rp.
Stirring was continued at a speed of m.

The Reynolds number at this time was 2.0×103.

Further, external cooling was performed so that the mother liquor temperature was 25.0+0.1°C.

After the addition was completed, the mixture was further aged for 60 minutes under the same conditions.

When this slurry was dehydrated by centrifugation at 900G for 3 minutes,
93.6. A cake of @ and a recovered mother liquor of 483.59 were obtained.

The concentrations of hydrogen peroxide and soda carbonate in the recovered mother liquor were 21.5 and 4.5, respectively. It was swt%.

Dry the cake at 60°C for 2 hours to obtain a dried cake of 89.
0. Got @.

The constituent particles were in the form of white granules, but they were not hollow, but had a double-layered structure with unreacted soda carbonate particles at the core.

The effective oxygen concentration was 5.3, which was extremely low compared to other examples, and the apparent density was 1.04, which was extremely high.

Comparative Example 3 A mother liquor of 1500 # containing soda carbonate, swt, 4.2 w of hydrogen peroxide, and the remainder water was added with 237.5 w of hydrogen peroxide solution. At the same time, addition of 287 tons of granular anhydrous soda carbonate, which had passed through 16 meshes and remained at 200 meshes, was started.

Both were added at a constant rate, and the addition of hydrogen peroxide was completed in 30 minutes and the addition of soda carbonate was completed in 60 minutes.

In this case, for 30 minutes after the start of addition, both components are added at a rate where the amount of soda carbonate added is smaller than the ratio of soda carbonate and hydrogen peroxide required to generate soda percarbonate.
The mother liquor composition gradually shifts to a higher concentration of hydrogen peroxide,
For example, the mother liquor composition 15 minutes after the start of addition is 7.
4 parts and 7.0'l of hydrogen peroxide), and 30 minutes later, they became 6.2 parts and 9.2 parts, respectively.

Therefore, in this case, most of the reaction for producing sodium percarbonate was carried out in a region with a high concentration of hydrogen peroxide outside the region of the mother liquor composition of the present invention.

After the addition was completed, aging was carried out for 30 minutes.

During this entire period, the temperature was maintained at 20°C by external cooling.
The temperature was controlled at +0.1°C.

A stirring blade with a diameter of 5.5 cm was used for stirring at 98 rpm.
It was held at m.

When the slurry was dehydrated by centrifugation at 900G for 3 minutes, 36
8.6. A @ cake and a 1650 @ mother liquor were obtained.

The final mother liquor composition is 8.2 parts each of soda carbonate and hydrogen peroxide,
I was in charge of 9.0.

The cake was dried at 60°C for 90 minutes to obtain 324t of white granules.

There were almost no hollow granules, and most of the granules were hollow granules with unreacted sodium carbonate granules as the core.

The effective oxygen concentration was 6.8, and the apparent density was 0.98.

Example 3 Hollow granular soda percarbonate was produced using a crystal habit modifier.

The additives in this example were in the form of magnesium sulfate 15. owt%, EDTA, 4Na42, Owt%, 3
Sodium silicate No. 38. This was an aqueous solution of Owt, which was added to the mother liquor in advance in the following manner.

That is, 192 tons of granular anhydrous soda carbonate was stirred and dissolved in about 1,100 liters of ion-exchanged water.

Add to this 60% hydrogen peroxide solution 102.5%. After adding @, if necessary, add No. 3 sodium silicate (38 many types) 9.92. @
, and/or EDTA, 4Na salt (42 items) 6.
43 y, and/or magnesium sulfate (item 15)
12.5. ＠ was added sequentially, and finally the total weight was reduced to 1500. @ closed.

Here, especially when adding magnesium sulfate, it was added gradually while stirring was continued to suppress the occurrence of scuttling.

While maintaining the temperature at 20℃±0.1℃, add 10% to this mother liquor.
0-24 mesh granular anhydrous soda 252.6
．． @ and 60. O preferential hydrogen oxide aqueous solution 202,! In 9
They were added simultaneously over 0 minutes.

During this time, stirring was continued at a Reynolds number of 1.0×104.

The resulting slurry was centrifugally dehydrated at 900 G for 3 minutes, and the resulting cake was dried at 60° C. for 120 minutes.

All of the produced granules were white crystalline and hollow.

In addition, since a considerable amount of fine crystals were generated, the morphology of the crystals was observed using a scanning electron microscope.

The dehydration properties of the cake depended on the morphology of the microcrystals, and plate-like crystals were more preferable than needle-like crystals.

The results obtained are shown in Table 2.

[Brief explanation of the drawing]

Figure 1 is a triangular diagram showing the phase diagram of a three-component system consisting of sodium carbonate, hydrogen peroxide and water; Figure 2 is a graph showing the particle size distribution of the raw material soda carbonate used in Example 1 and the resulting granules;
FIGS. 3 and 4 are microscopic photographs of the hollow granules obtained in Example 2, with FIG. 3 being a plan view and FIG. 4 being a cross-sectional view.

Claims (1)

[Scope of Claims] 1. A hollow granular percarbonate whose interior is hollow and whose shell portion is composed of crystalline percarbonate. 2. The hollow granular percarbonate according to claim 1, wherein the shell portion is a plate-like or needle-like crystal percarbonate. 3. Hollow □ granular percarbonate according to claim 1 or 2, which has an average particle diameter of 100 to 2000μ. 4. The hollow granular percarbonate according to any one of claims 1 to 3, wherein the percarbonate is sodium percarbonate. 5 Prepare an aqueous mother liquor solution containing 6.0 to 15.0% by weight of carbonate and 1.5 to 6.0% by weight of hydrogen peroxide, and change the composition of this aqueous mother liquor solution to 6.0 to 15% by weight of carbonate.
．． 0% by weight and hydrogen peroxide from 1.5 to 6.0% by weight
The percarbonate is crystallized by adding granular carbonate and an aqueous hydrogen peroxide solution at the same time or alternately at a ratio such that the amount of carbonate is maintained within the range of 2 moles or more per 3 moles of hydrogen peroxide. A method for producing hollow granular percarbonate, the method comprising: 6 The mother liquor aqueous solution composition to be maintained is 7.0 to 13.0% by weight of carbonate and 3.0 to 5.0% by weight of hydrogen peroxide.
A method for producing a hollow granular percarbonate according to claim 5. 7 The average particle size of the granular carbonate to be added is 50 to 20
A method for producing a hollow granular percarbonate according to claim 5 or 6, wherein the hollow granular percarbonate has a particle size of 00μ. 8. Hollow granular filter according to claim 7, in which granular carbonate and hydrogen peroxide aqueous solution are added simultaneously and continuously, and the crystallized percarbonate is continuously or intermittently extracted from the reaction system. Method for producing carbonates. 9. The method for producing a hollow granular percarbonate according to any one of claims 5 to 8, wherein the carbonate is carbonate. 10 Na of ethylenediaminetetraacetic acid in mother liquor aqueous solution
# The method for producing hollow granular percarbonate according to any one of items 5 to 9, which comprises adding Ca or Mt salt and phosphate and/or silicate.